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    STP674

    Design, Fabrication, and Nondestructive Evaluation of an Advanced Composite Foil Test Component (Tapered Box Beam)

    Published: 01 January 1979


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    Abstract

    A foil test component (tapered box beam) consisting of hybrid graphite/epoxy skins and HY-130 steel spars was designed and fabricated. This design is representative of a hydrofoil strut/foil system having an approximate 25 percent weight savings compared to current metallic strut/foil systems fabricated entirely of steel with a yield strength of 900 MPa. Two identical box beams will be tested in the laboratory (one in air, the other in salt water) to assess the fatigue behavior of a typical graphite/epoxy structure under simulated sea loads and to compare its behavior with current metal designs.

    The graphite/epoxy hybrid (T-300, GY-70 fibers) laminate selected for the skin material has been characterized; the elastic constants and ultimate strengths were in excellent agreement with the theoretical results predicted during the preliminary design phase. An in-depth joint evaluation was conducted as the next step of design verification. Each type of joint was modeled and tested statically and in fatigue. Although a maximum joint efficiency of 98 percent was developed in the I-beam tests, the scarf joint tests led to a 33 percent reduction in the design ultimate stress allowable for the composite material. One box beam has been successfully fabricated and assembled. A comprehensive nondestructive evaluation of the components and finished assembly reveal no detectable defects as a result of laminate fabrication or box beam assembly.

    Keywords:

    composite materials, fatigue tests, graphite composites, epoxy laminates, mechanical properties, nondestructive tests, joints, hybrid composites, ultimate strength, elastic properties, property prediction


    Author Information:

    Greszczuk, LB
    Principal engineer/scientist, McDonnell Douglas Astronautics Company, Huntington Beach, Calif.

    Couch, WP
    Structural engineer, David W. Taylor Naval Ship Research and Development Center, Bethesda, Md.


    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP36904S